Surface acoustic wave (SAW) devices use surface waves propagated on the surface of an elastic solid for electronic signal processing. A typical SAW device uses a transducer to convert electromagnetic signal waves, which travel at the speed of light, to acoustic signal waves traveling at speeds on the order of 10.sup.5 less than the speed of light. This substantial reduction in wavelength allows designers to implement certain complex signaling processing functions in a significantly smaller space than would be needed for traditional circuit designs. Thus, a SAW device designed to handle complex signal processing functions can offer considerable cost and size advantages over competing technologies. SAW technology is increasingly found in applications such as filters, resonators, oscillators, delay lines, and other similar devices.
SAW devices are typically implemented on a piezoelectric substrate and usually employ interdigitated transducers (IDTs) located on the surface of the piezoelectric substrate to generate and detect acoustic waves. The geometry of the IDTs on the piezoelectric substrate plays a significant role in the signal processing and frequency response characteristics of a SAW device. Changes in temperature may also affect the operation of the device. SAW device designers generally achieve the desired frequency response of the device by focusing on the geometry of the IDTs, and by the choice of materials used for the piezoelectric substrate.
Once the design parameters are chosen for a SAW device, the device may operate satisfactorily under certain conditions, but may fail to properly perform as the operating environment changes. For example, a SAW device may fail to operate because of adverse effects of temperature on the material of the device. To compensate for the operating environment dependency of the SAW devices, designers have tended towards more complex designs. SAW device performance is also affected in other ways. For example, variations in the process used to manufacture a SAW device may affect its operating characteristics, and depending on the application, compensating adjustments to the device may be needed.
Performance degradation of SAW devices as a result of varying operating conditions in the field can lead to poor performance and even field failures. Designs which focused on more complex IDT geometries can improve performance, but may result in an increase in manufacturing cost and complexity. The ability to tune SAW devices to account for operating conditions or for manufacturing variations is rather limited in the art. Consequently, there exists a need in the art to address manufacturing variations and operating conditions dependency of SAW devices.